Nogales has been the epicenter for cross-border drug tunnels for years. U.S. authorities have found 100 drug tunnels in that city since 1990, more than any other location along the 2,000-mile United States-Mexico border.

But the tunnel found this week tops them all. At 481 feet, longer than 11/2 football fields, it is the longest ever discovered in Nogales, according to Immigration and Customs Enforcement officials.

The tunnel extended from a house in Nogales, Sonora, to a house in Nogales, Ariz., and was being used to smuggle marijuana and other drugs into the U.S., ICE officials said.

Federal authorities found a half pound of heroin and 46 pounds of marijuana inside.

They seized another 590 pounds of marijuana after stopping a vehicle federal agents saw driving away from the house in Nogales, Ariz., on Monday.

The house was under surveillance by a multiagency task force created in 2012 to find and dismantle drug tunnels.

The driver of the truck, Jesus Alberto Ramirez-Valencia, 22, a U.S. citizen from Nogales, Ariz., and two Mexican citizens, Jose Mario Armenta-Valdez, 41, and Jose Solorzano-Flores, 41, were charged with drug conspiracy.

The driver was apparently transporting the drugs to a second house where Solorzano-Flores was found outside, authorities say. Armenta-Valdez was arrested after federal agents raided the house, where an opening to the drug tunnel leading into the U.S. from Mexico was found.

Eric Balliet, assistant special agent in charge of ICE’s Homeland Security Investigations in Nogales, said drug smugglers are resorting to tunnels because of tighter border security.

“If a drug-trafficking organization can establish a well-manufactured tunnel, the likelihood of a law-enforcement encounter is somewhat slim,” Balliet said. “You don’t run the risk of exposing your dope above ground, whether it’s human backpackers or smuggling through the port or over the fence. It’s completely concealed from start to finish.”

The drug tunnel found Monday is the third uncovered in Nogales since December.

Since 1990, 169 tunnels have been found along the southern border, 100 of them in Nogales.

Last fiscal year, six of the seven tunnels found along the U.S.-Mexico border were found in Nogales. In 2012, seven of the 16 tunnels found on the border were in Nogales, and 12 of the 18 the year before that, according to U.S. Customs and Border Protection.

Nogales is popular for drug tunnels because smugglers can tap a vast underground drainage system that connects the border cities, Balliet said.

Once inside the drainage system, smugglers bore spider tunnels into the U.S., he said

The two cities also have large neighborhoods close to each other, making it easy for smugglers to dig tunnels from a house on the Mexican side to a house on the U.S. side, he said.

The tunnel found Monday stretched 70 feet from a house in Nogales, Sonora, to the U.S. border and then another 411 feet to a house in Nogales, Ariz., ICE officials said.

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